PCSK9 and hyperlipidemia: We performed an in vivo macrophage foam cell formation assay in the peritoneum of Fmr1−/− and Fmr1+/+ mice, using a well‐established method in which we induced hyperlipidemia using a combination of adenoviral‐delivery of proprotein convertase subtilisin kexin 9 (AAV_PCSK9), a protein that directs hepatic low‐density lipoprotein (LDL) receptors for degradation, and feeding with WD for 16 weeks (Li et al, 2007; Tsimikas et al, 2011; Peled et al, 2017).